1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to controlling transmission rate, and more particularly, to controlling transmission rate by using error correction packets.
2. Description of the Related Art
Recently, there has been an increasing demand for a real-time data transmission of multimedia data or voice communication on the existing networks.
With the advancements in communication and network technologies, network communication over wireless network environments using radio signals of various frequency bands has been making a widespread implementation to the existing cable-based network environments using coaxial or optical cables.
Unlike the cable-based networks, data transmission channels in wireless networks are not physically fixed. Thus, wireless networks have a limited bandwidth range compared to the cable-based networks, and have a variable traffic property often affected by the mobility of a communication apparatus and by the changes in radio link properties. As a result, in wireless networks, there is a high packet-loss rate compared to the cable-based networks.
Although communication apparatuses can transmit packets within the primary network frequency band, the frequency band decreases with the increased use by customers, resulting in a network instability that makes it difficult to ensure stable packet transmission.
Typically, packet loss occurring in wireless networks results from an inadequate bandwidth or from characteristics of radio link. When packet loss is caused by decreased bandwidth, transmission rate needs to be reduced. However, temporary packet loss is generally caused by the characteristics of radio link, and there is no need to reduce the transmission rate as in the case of decreased bandwidth. That is, when transmitting real-time data such as streaming content, it is important to assure a stable real-time data transmission by maintaining the transmission rate than to reduce the transmission rate for compensating the temporary packet loss. Accordingly, once a packet loss occurs, it is important to determine the cause to appropriately control the transmission rate.
Conventionally, the packet adjacent to a packet transmitted in a longer transmission time than expected, by a relative one-way round-trip time (ROTT), was presumed to be lost, which was considered as an instability loss. To compensate this loss, a process of re-transmitting a response packet to the transmitted packet and lost packet is conventionally required. However, such a process falls short of being adequate for the real-time transmission.
In International Patent Publication No. WO 01/84731 A1, entitled “Methods and systems for forward-error-correction-based loss recovery for interactive video transmission,” discloses an error correction technique for dealing with the packet loss occurring during multimedia data transmission. However, the above invention does not disclose a method of dealing with a frequent and unavoidable situation of losing a large number of serial packets caused by decreased bandwidth.